SEPARATION OF PLASMA COMPONENTS FROM BLOOD CELLS
Various diagnostic methods are based on the determination of the concentration of analytes in blood plasma. Often, however, the blood cells seriously disturb the assay procedure chosen and therefore it is necessary to separate the blood cells from the plasma prior to the measurement. In most cases plasma is separated by centrifugation. Although centrifugation is considered to be a routine method a device and tubes are required affecting the level of test costs. Moreover, centrifugation is a laborious step to perform. Furthermore, test tubes broken and aerosoles produced during centrifugation cause a risk of infection for the laboratory personnel.
Filtration methods are also used in some degree. However, their volumetric capacity is very low and they can be performed most satisfactorily in special applications like immunochromatography.
Methods for separation of plasma from blood components using agglutination (DE 2038722, DE 1498577) or agglutination-filtration (EP-183991 A1, EP-045476 A1, EP-0194502 B1) have been disclosed earlier. Said methods or devices are intended for narrow-segmented special applications, either as a primary plasma separation method, where the separated plasma is physically transferred into another tube or cuvette for analysis or transported by capillary forces into another membrane layer or device chamber. The purpose of these methods differ from the purposes presented in this invention. Both the production methods and the methods of use of the agglutinating component are different from those disclosed in this invention.
According to the literature potato (Solanum tuberosum) contains STA-lectin (Solanum tuberosum agglutinin) and various other carbohydrate binding proteins, which have not been completely characterized so far (Kilpatrick, D. C., Biochem. J. 1980, 191:273-275; Allen, A. K. and Neuberger, A., Biochem. J. 1973, 135:307-314; Matsumoto, I. et al., J. Biol. Chem. 1983, 258:2886-2891; Millar, D. J. et al., Biochem. J. 1992, 283:813-821). Carbohydrate binding proteins isolated from other plants and those produced by means of recombinant technology and genetic engineering may also be used. It is of importance that irrespective of the production procedure, the carbohydrate binding proteins produced all bind blood cells but not plasma glycoproteins.
The STA-lectin binds to blood cell surface antigens of various animal species, including human. The agglutination procedure is based on the binding of polyvalent lectin to cell surface carbohydrate moieties of the blood group antigens. The STA-lectin is specific for N-acetyl-D-glucosamine-oligomers but shows only minor affinity to N-acetyl-D-glucosamine-monomers or other sugar monomers or polymers.